ssb: fix init regression with SoCs

This fixes a Data bus error on some SoCs. The first fix for this
problem did not solve it on all devices.
    commit 6ae8ec27
    Author: Rafał Miłecki <zajec5@gmail.com>
    Date:   Tue Jul 5 17:25:32 2011 +0200
        ssb: fix init regression of hostmode PCI core

In ssb_pcicore_fix_sprom_core_index() the sprom on the PCI core is
accessed, but the sprom only exists when the ssb bus is connected over
a PCI bus to the rest of the system and not when the SSB Bus is the
main system bus. SoCs sometimes have a PCI host controller and there
this code will not be executed, but there are some old SoCs with an PCI
controller in client mode around and ssb_pcicore_fix_sprom_core_index()
should not be called on these devices too. The PCI controller on these
devices are unused, but without this fix it results in an Data bus
error when it gets initialized.

Cc: Michael Buesch <m@bues.ch>
Cc: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>